Obviously the risk/reward ratio would depend greatly on the political climate of that moment in state history.  With all delegates being elected at once, the convention would be a true snapshot of the mood of the state - which does seem a very dangerous thing at first glance.  I much prefer the checks and balances and overlapping terms of the usual system, which serves to minimize the effect of electorate mood-swings.

Still, I wouldn't be surprised to see a retreat toward conservatism right around '10, based on the over-reaching first four months of this Presidency and Congress, in which case a Con-con could (though still risky) actually lean in the Conservatives' favor.